This invention relates to electronic device component assemblies of the type having multiple riser printed circuit boards (PCBs) connected in a vertical orientation to a horizontally-extending main or mother PCB. More particularly, the present invention relates to a new and improved structure and method for retaining the vertically-oriented riser PCBs against vertical separation from an edge connector and from lateral side-to-side movement, as might occur during use, shipment or transportation. The present invention also relates to ducting cooling air over heat-sensitive electronic components to achieve improved cooling.
Many electronic devices use a mother PCB known as a motherboard as a foundation upon which the other electronic components are attached and interconnected. The other electronic components typically include integrated circuit (IC) chips, microprocessors, memories, interfaces for communicating with external devices, and the like. Typically the motherboard contains the electronic components necessary to achieve the basic functionality of the electronic device. The motherboard is usually retained within a rigid cabinet or housing of the device. If the electronic functionality of the device is not overly complex, or if there is sufficient space within the cabinet or housing, the motherboard may be sufficiently large to retain and connect all of the electronic components necessary to achieve enhanced functionality beyond the basic functionality. In many cases however, it is necessary to enhance the functionality of the electronic device beyond the capability of the components of the motherboard. For example, computer motherboards usually have connectors to add additional memory chips and thereby increase the memory capacity of the computer.
Connecting an additional PCB to the motherboard enhances the functionality because of the increased functional capacity of the components of the additional PCB. Such additional PCBs are sometimes referred to as xe2x80x9criser boards,xe2x80x9d because riser boards typically extend at an angle perpendicular to the motherboard in order to utilize the space above the motherboard within the cabinet. The riser boards are connected to the motherboard by a conventional edge connector. The edge connector includes a multiplicity of individual electrical contacts and receptacles which receive and electrically connect to conductor pads formed along a bottom edge of the riser board. It is not unusual that from two to twelve edge connectors may be attached to the motherboard in order to connect a corresponding number of riser boards. When connected to the motherboard, the riser boards usually extend parallel to one another.
In addition to providing the opportunity to increase the functionality of the motherboard by connecting additional riser boards, the edge connectors allow the riser boards to be removed and replaced in relatively easy manner. The riser boards can be separated from the edge connectors by pulling the riser boards vertically away from the motherboard. The ability to easily remove and replace the riser boards is an advantage when it is desired to change the riser board to alter the functionality or capability of the electronic device, or to replace defective parts.
Because the riser boards extend perpendicularly with respect to the motherboard, it is necessary to support the riser boards to prevent them from lateral, side-to-side pivoting movement about a bottom edge connector. Electronic devices are subject to forces when they are transported, and some electronic devices that are incorporated in movable equipment are subject to continued forces from use of the device itself. Lateral pivoting movement of the riser boards has the potential of fatiguing the electrical edge connectors, which could result in electrical disconnection or breakage and consequent failure of the electronic components. The riser boards could also laterally tilt to contact one another and possibly create unintended electrical connections that would adversely affect the performance of the electronic device.
To retain the riser boards against the lateral side-to-side movement, it has been typical to use vertical card guides. Vertical card guides are positioned to retain the opposite vertically extending edges of each end of a full-length riser board. With the opposite vertical edges retained in the card guides, the riser board is prevented from pivoting in lateral side-to-side movement. However, the lengths of the riser boards may vary. Riser boards of three-fourths or half length are commonly used. Since the vertical card guides are set to accommodate only a full-length riser board, reduced-length riser boards cannot be supported at both vertically- extending opposite edges. Reduced-length riser boards can only be supported at one vertical edge by one vertical card guide. The other vertical edge cannot be supported, because the reduced-length of the riser board terminates the other vertical edge at a location separated from the location of the other vertical card guide. The other, unsupported edge is therefore free to move laterally with side-to-side movement. Consequently, reduced-length riser boards may not be adequately supported, and are subject to the risks of premature failure due to movement during, use transportation or shipping of the electronic device.
The vertical card guides also do not retain the riser boards against movement in a vertical plane away from the edge connector attached to the motherboard. Such vertical movement may also result from the vibration and motion associated with transportation or use. Sufficient vertical movement can disconnect the riser boards from the edge connectors on the motherboard, thereby disabling the functionality achieved by the riser board.
Another potential difficulty associated with electronic devices is ensuring adequate air flow to cool heat-sensitive electronic components. The position of the electronic components relative to the cooling air flow is critical, to assure adequate air flow over and cooling of those components. Positioning the heat-sensitive components relative to the airflow sometimes restricts the ability to utilize efficiently the available space of the motherboard to accommodate other less heat-sensitive electronic components. The vertically extending riser boards may tend to channel or direct the cooling air which normally flows over the motherboard.
The use of riser boards with motherboards in the manner described, and other background considerations, have given rise to the present invention.
One improvement of the present invention involves retaining riser boards relative to the motherboard in a manner which prevents lateral side-to-side movement and which retains the riser boards against vertical movement which would separate the riser board from its connection at the edge connector to the motherboard. Another improvement involves retaining the riser boards while preserving the advantages of the vertical orientation and edge connection that allows easy access to and removal of the riser boards. Another improvement of the present invention involves retaining the riser boards in the manner described while ducting cooling air flow to achieve enhanced cooling in locations where critical heat-sensitive and heat-generating electronic components of the motherboard are located. The present invention obtains these improvements without requiring the use of special tools to gain access to the riser boards for their removal and insertion or to retain the riser boards.
These and other improvements are achieved by a structure for retaining a vertically-extending riser board connected to an edge connector of a horizontally-extending motherboard of an electronic device. The riser board has an upper horizontal edge and the lower horizontal edge, and the lower horizontal edge is connected to the edge connector. The retaining structure comprises a plate having a horizontal portion, a resilient compressible gasket attached to the horizontal portion of the plate, and a positioning structure which locates the plate in a closed position relative to the riser board. In the closed position, the horizontal portion of the plate is located above the upper horizontal edge of the riser board to retain the riser board. The gasket is resiliently compressed against the upper horizontal edge of the riser board to retain the riser board against lateral side-to-side movement and against vertical movement. The lateral side-to-side movement of the riser board, which might fatigue or otherwise compromise the electrical connection at the edge connector, is avoided. Vertical movement of the riser board relative to the motherboard, which could disconnect the riser board from the edge connector, is also avoided.
The improvements of the present invention are also realized in a method of retaining the vertically-extending riser board against vertical and lateral side-to-side movement. The retaining method comprises the steps of connecting the riser board to an edge connector of the horizontally-extending motherboard of the electronic device, locating a plate having horizontal portion in a closed position relative to the riser board where the horizontal portion of the plate is above the upper horizontal edge of the riser board, and compressing a resilient gasket between the horizontal portion of the plate and the upper horizontal edge of the riser board to retain the riser board against vertical movement and against lateral side-to-side movement.
Preferable aspects of the retaining structure and retaining method involve locating the plate in open position where the horizontal portion of the plate and the gasket are laterally withdrawn to a non-interfering position to allow the riser board to be vertically inserted and removed from the edge connector. Preferably, the plate is pivotally attached at a location laterally separated from the riser board to pivot into the non-interfering open position and into the retaining closed position. The plate preferably includes a center portion which is pivotally connected at a location laterally separated from the riser board, and the horizontal portion extends from the center portion toward the riser board and pivots between the non-interfering open position and the retaining closed position.
Another preferable aspect of the retaining structure and the retaining method involves directing a cooling air flow over the motherboard and the riser boards. The plate includes a transition portion which extends between a center portion and horizontal portion, and the center portion is positioned vertically below the upper horizontal edge of the riser board. The transition portion extends from the center portion upwardly in the direction toward the riser board to the horizontal portion. A vertical dimension between the center portion and the motherboard defines a space through which the cooling air flows over the motherboard and the riser board. The motherboard includes heat-sensitive electronic components which are located adjacent to the space defined between the center portion and the motherboard. A smaller cross-sectional size of the space between the center portion and the motherboard increases the speed of the cooling air flow over the heat-sensitive components of the motherboard located within that space. Preferably, the plate also includes a baffle portion which extends into the cooling air flow to duct the cooling air flow into the smaller cross-sectional space to further enhance the cooling air flow through that space. After passing over the heat sensitive elements, the transition portion of the plate ducts the cooling air flow from the space into a flow path of increasing cross-sectional size.
Other preferable aspects of the retaining structure and retaining method involve simultaneously retaining a plurality of different-length riser boards. The length of each riser board extends in a horizontal direction between opposite vertically-extending end edges. The horizontal portion of the plate extends above the upper horizontal edge of the different-length riser boards to retain the different-length riser boards against vertical separation and lateral side-to-side movement. The retention force applied to the upper horizontal edge is not dependent on the length of the riser boards, and therefore accommodates a plurality of different-length riser boards without requiring a card guide connected to both vertically extending end edges of the two riser boards.
A more complete appreciation of the present invention and its scope may be obtained from the accompanying drawings, which are briefly summarized below, from the following detail descriptions of presently preferred embodiments of the invention, and from the appended claims.